In the field of digital image graphics, an image gradient is a directional change in color (often termed a color gradient) and/or intensity of an image along one or more directions of picture elements (pixels). An image gradient may be applied to the entirety of an image or a portion thereof. One example of an image gradient is a one-dimensional gradient, in which the gradient causes a change in color or intensity of the image along a single direction or axis. In many cases, a one-dimensional gradient is aligned either vertically or horizontally relative to an orientation of an observer of the gradient, although diagonal orientations for one-dimensional gradients are also possible. In some implementations, the gradient may be based on a continuous density function, wherein the color and/or intensity of each of the pixels of a digital image are associated with a corresponding value of the function.
Another example of an image gradient is a two-dimensional image gradient, in which the color and/or intensity of an image change along two directions. In many instances, the two directions are orthogonal, such as vertically and horizontally, or diagonally to the left and diagonally to the right. However, two-dimensional image gradients are not necessarily so constrained, and may be aligned along any two axes of a two-dimensional image that are not necessarily orthogonal.
Image gradients have often been employed in graphical user interfaces (GUIs) of any number or type of electronic devices, such as desktop computers, laptop computers, game systems, set-top boxes, tablet computers, smart phones, and so on. Further, image gradients may be employed to provide realistic features, such as shadows, to an image, or merely to provide some visual interest to the image.